20 Chapter 1 this, the authors of both studies concluded that MRA could be used as the primary, and in most cases, the only modality before surgical treatment. It must be noted that both studies used TOF MRA and failed to evaluate the feasibility of endovascular treatment. It is clear that a study evaluating the efficiency of a non-invasive modality to assess coilability of an aneurysm was needed, and we carried out such a study upon the group of patients described in Chapter 2. This study is described in Chapter 3: Performance of Contrast Enhanced Magnetic Resonance Angiography in patients presenting with Subarachnoid Hemorrhage. Part 2: predicting suitability of aneurysm for endovascular coiling. The true value of a non-invasive modality to assess the coilability of an aneurysm is difficult to determine, firstly because coilability is a largely subjective criterion,272-274 and secondly because the possibilities for endovascular treatment are rapidly evolving.275 Thus aneurysms that were not suitable for endovascular treatment ten years ago can now be treated with the aid of balloons276 or stents,277,278 or with so-called flow diverters.279,280 Only recently was the clinical value of TOF MRA for therapeutic planning in patients with SAH investigated using DSA as the gold standard.272 A treatment plan based on the TOF MRA was made for 165 patients, who subsequently underwent DSA: only 10 treatment strategies were altered as a consequence of DSA findings. We used the data from the group of patients described in Chapters 2 and 3 to simulate CEMRA as the sole modality used to select patients for endovascular treatment and evaluated diagnostic, therapeutic and financial consequences of different diagnostic strategies. This study is described in Chapter 4: Simulation employing different scenarios using contrast-enhanced MRA (CEMRA) and digital subtraction angiography (DSA) in patients presenting with a subarachnoid hemorrhage (SAH). Treatment Reports of neurosurgical treatments of intracranial aneurysms first appeared in the late 19th century, and mostly involved ligation of the parent vessel.281,282 The first planned intracranial aneurysm operation was carried out in 1931 by Dott, during which he successfully wrapped an aneurysm that had bled three times.283 Six years later the first aneurysm clipping procedure was performed by Dandy.284 Subsequent advances in neurosurgical techniques (such as the development of operating microscopes, microsurgical instruments, improved clips, neuroanaesthesia, and perioperative management for complications) enabled neurosurgeons to treat most cerebral aneurysms, and surgical aneurysm clipping remained the predominant treatment for almost four decades.285 In the second half of the 19th century, aortic aneurysms were treated by metal wiring.286 Wire, the theory stipulated, would promote thrombus formation and reduce flow into the aneurysm sac. Moore introduced 26 yards of coil into a thoracic aorta aneurysm in his first such operation in 1864.287 In the same period other physicians experimented with electrothrombosis (electropuncture or
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